
#include <string.h>
#include "ev_packet.h"

static const uint8_t crc16_table_hi[] = {
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40
};

static const uint8_t crc16_table_lo[] = {
    0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7,
    0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E,
    0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9,
    0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
    0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
    0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32,
    0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
    0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38,
    0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF,
    0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
    0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
    0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4,
    0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB,
    0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
    0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
    0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0,
    0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97,
    0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
    0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89,
    0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
    0x41, 0x81, 0x80, 0x40
};


/* modbus crc16, initial value 0xffff */

uint16_t ev_crc16( const uint8_t* data, uint32_t datalen, uint16_t crc_in)
{
    uint8_t crc_hi;
    uint8_t crc_lo;
    uint16_t result;
    int index;

    if (datalen <= 0)
    {
        return 0;
    }

    crc_hi = (crc_in>>8) & 0xff;
    crc_lo = crc_in & 0xff;

    while( datalen-- )
    {
        index = crc_lo ^ *( data++ );
        crc_lo = ( uint8_t )( crc_hi ^ crc16_table_hi[index] );
        crc_hi = crc16_table_lo[index];
    }

    result = crc_hi;
    result <<= 8;
    result += crc_lo;

    return result;
}


int ev_parser_init(ev_parser_t *parser,
                   void *arg,
                   void (*cb)(const ev_parser_t *, const ev_packet_t *)
)
{
    memset(parser, 0, sizeof(ev_parser_t));
    parser->arg = arg;
    parser->cb = cb;
    parser->crc = EV_PACKET_MAGIC;
    return 0;
}

int ev_parser_reset(ev_parser_t *parser)
{
    parser->offset = 0;
    parser->crc = EV_PACKET_MAGIC;
    return 0;
}

static int _check_tail(const uint8_t *data, uint32_t len)
{
    if (len < EV_PACKET_TAIL_LEN) {
        return -1;
    }
    if (data[len - 10] != EV_PACKET_SOF) {
        return -2;
    }
    uint32_t cal_len = data[len - 4];
    cal_len <<= 8;
    cal_len += data[len - 5];
    if (cal_len != len - EV_PACKET_TAIL_LEN) {
        return -3;
    }

    uint8_t sum = 0;
    for (uint32_t i = len - EV_PACKET_TAIL_LEN; i < len - 2; i ++) {
        sum += data[i];
    }
    if (sum != 0) {
        return -4;
    }

    return 0;
}

int ev_parser_feed_one(ev_parser_t *parser, uint8_t data)
{
    if (parser->offset >= EV_PACKET_MAX_LEN) {
        ev_parser_reset(parser);
    }
    parser->buf[parser->offset ++] = data;
    parser->crc = ev_crc16(&data, 1, parser->crc);
    if (!parser->crc && _check_tail(parser->buf, parser->offset) == 0) {
        if (parser->cb && parser->offset >= EV_PACKET_TAIL_LEN) {
            ev_packet_t packet;
            packet.user = parser->buf[parser->offset - 9];
            packet.seq = parser->buf[parser->offset - 8];
            packet.cmd = parser->buf[parser->offset - 6];  // cmd high byte
            packet.cmd <<= 8;
            packet.cmd += parser->buf[parser->offset - 7]; // cmd low byte
            packet.len = parser->offset - EV_PACKET_TAIL_LEN;
            memcpy(packet.data, parser->buf, packet.len);
            parser->cb(parser, &packet);
        }
        ev_parser_reset(parser);
    }
    return 0;
}

int ev_parser_feed(ev_parser_t *parser, const uint8_t *data, uint32_t len)
{
    for (uint32_t i = 0; i < len; i++) {
        ev_parser_feed_one(parser, data[i]);
    }
    return 0;
}

int ev_packet_make(const ev_packet_t *pkt, uint8_t *data, uint32_t *len)
{
    uint32_t cal_len = 0;
    uint8_t chksum = 0;
    if (pkt && data && len && pkt->len <= EV_PACKET_MAX_DATA_LEN) {
        memcpy(data, pkt->data, pkt->len);
        cal_len += pkt->len;

        data[cal_len ++] = EV_PACKET_SOF;  // sof
        data[cal_len ++] = pkt->user;      // user
        data[cal_len ++] = pkt->seq;       // seq
        data[cal_len ++] = (pkt->cmd & 0xff); // cmd low byte
        data[cal_len ++] = (pkt->cmd >> 8) & 0xff; // cmd high byte
        data[cal_len ++] = (pkt->len & 0xff); // len low byte
        data[cal_len ++] = (pkt->len >> 8) & 0xff; // len high byte

        for (uint32_t i = cal_len - 7; i < cal_len; i ++) {
            chksum += data[i];
        }
        data[cal_len ++] = (~chksum) + 1;   // chksum

        uint32_t crc = ev_crc16(data, cal_len, EV_PACKET_MAGIC);
        data[cal_len ++] = crc & 0xff;
        data[cal_len ++] = (crc >> 8) & 0xff;
        *len = cal_len;
        return 0;
    }

    return -1;
}

int ev_packet_check(const uint8_t *data, uint32_t len, ev_packet_t *pkt)
{
    if (!data || len < EV_PACKET_TAIL_LEN || len > EV_PACKET_MAX_LEN) {
        return -1;
    }
    if (ev_crc16(data, len, EV_PACKET_MAGIC)) {
        return -2;
    }
    if (_check_tail(data, len)) {
        return -3;
    }
    if (pkt) {
        pkt->user = data[len - 9];
        pkt->seq = data[len - 8];
        pkt->cmd = data[len - 6];  // cmd high byte
        pkt->cmd <<= 8;
        pkt->cmd += data[len - 7]; // cmd low byte
        pkt->len = len - EV_PACKET_TAIL_LEN;
        memcpy(pkt->data, data, pkt->len);
    }
    return 0;
}
